Alarm system



p 3,264,626 lc Patented Aug 2, 1966 poration of (Ianada Filed Aug. 1, 1963, Ser. No. 299,232 Claims. ((81. MEL-213.1)

This invention relates to an annunciator and alarm system and, more particularly, to such a system including electroluminescent indicating panels and control means therefor.

Alarm or annunciator systems are extensively used in a variety of industrial applications to monitor process conditions, the operability of drive and control components, and innumerable other variable factors. In general, these systems include annunciator or alarm means controlled by field contacts that respond to the condition to be monitored to provide audible and visible indications, usually of abnormal conditions. The alarm or annunciator and the controls therefor are frequently manufactured in modular form using tiags or needles controlled by mechanical movements or means requiring incandescent lamps, such as back lighted name plates, as indicating means. However, these modules frequently are heavy and cumbersome and require extensive installation space. The energy consumed as well as the heat radiated by a number of these prior art units is excessive, and the construction and fabrication of these units is not well adapted to modern production line techniques.

Accordingly, one object of this invention is to provide a new and improved alarm or annunciator system.

Another object is to provide an alarm or annunciator system including electroluminescent indicating means.

Another object is to provide an annunciator system module which is easily fabricated using semiconductor components and which is of reduced size and weight.

A further object is to provide new and improved means for controlling visible and .audible indicating means to provide different types oi alarm indications.

Another object is to provide an iannunciator or alarm system including an electroluminescent indicating panel that is selectively supplied with a high frequency energy under the control of a gated rectifier that is periodically supplied with operating signals from a pulse source controlled by a monitored conditon responsive control means.

In accordance with these and many other objects, an embodiment of the present invention comprises an electroluminescent panel adapted to be supplied with high frequency energy under the control of a gated silicon rectifier. The control electrode or gate of the gated rectifier is selectively supplied with operating signals from a multivibrat-or or a bistable circuit that is normally maintained in an inoperative state. When an abnormality arises in the condition to be monitored, an enabling signal is supplied to the multivibrator, and the gated rectiiier is placed in conduction to energize the electroluminescent panel. The illumination of the panel by high frequency potential provides an indication of the abnormal condition. The control circuit for the multivibrator includes means adjustable to diiferent settings to provide difierent types of audible alarms and continuous or flashing illumination of the panel varying in accordance with the persistence of the abnormal condition.

'Many other objects and advantages of the present invention will become apparent from considering the following detailed description in conjunction with the single sheet of drawing which illustrates a schematic circuit diagram of an alarm or annunciator system embodying the present invention.

Referring more specifically to the drawing, therein is illustrated an alarm or annunciator control system, indicated generally as 19, which embodies the present invention and which includes as an output indicating means an electroluminescent panel 12 that is selectively energized from a 500 c.p.s. potential source 14 under the control of a gated rectifier 16 to provide either intermittent or continuous illumination. The rectifier 16 is supplied With control signals, either pulsed or continuous, by a multivibrator which is indicated generally by the reference number 18. An input stage, indicated generally as 20, responds to the establishment of an abnormality in the condition to be monitored and, together with an interposed control means 22, controls the mode of operation of .the multivibrator 18. The control means 22 also provides an audible indication of an abnormality and is adjustable to permit the circuit or system 10 to provide different types of audible and visible alarms varying in accordance with the persistence of the abnormal condition.

The input stage 20 is controlled by the field or trouble contacts to provide an electrical output signal representing the existence of or the establishment of an abnormal or alarm condition. The input stage 20 includes a normally nonconductive transistor 24, the collector electrode of which is connected to a positive potential source of a nominal 12 volts and the emitter of which is connected to a negative potential source of a nominal 12 volts through a resistor 26. The input stage 20 is adapted to respond to alarm or abnormal conditions indicated by either the opening of a pair of normally closed contacts 28 or by the closure of a pair of normally open contacts 30. More specifically, if the contacts 30 are to be used as the control means, the contacts 28 are opened. Thus, when the contacts 30 are closed because of an abnormal operating condition, the volt-age dividing network connected between the positive and negative potential sources and including not only the resistance 26 but also a pair of additional resistance elements 32 and 34 biases the base of the transistor 24 positive with respect to its emitter so that the transistor 24 is placed in a conductive condition to supply a positive-going signal from the input stage 20 representing the existence of the trouble condition. Similarly, if the alarm condition is to be indicated by the opening of the normally closed contacts 28, the switch 30 is maintained in a closed condition together with the switch or contacts 28. The closed contacts 28 maintain the base of the transistor negative with respect to its emitter despite the closed contacts 30. Thus, when the abnormal operating condition arises and causes the opening of the contacts 28, the transistor 24 is placed in a conductive condition in the manner described above to provide a positive-going output signal.

The positive-going output signal from the input stage 20 is forwarded to the control means 22 and is differentiated in a network including a capacitance 36 and a resistance 38 to provide a positivegoing pulse or spike that is applied to the base electrode of a normally nonconductive transistor 40 through a diode 42. The collector of the transistor 40 is connected through a resistance element 44 to a switch 46 that is operated to close either a pair of contacts 46a or a pair of contacts 46b in dependence on the type of alarm indication to be provided by the circuit 10. The closure of the contacts 46a provides an operating potential for the transistor 40 which persists for only so long as the transistor 24 in the input stage 20 remains in a conductive condition. Alternatively, when the contacts 46b are closed, the collector of the transistor 40 is permanently connected to a positive operating potential through the resistance 44.

Therefore, when the positive-going pulse is coupled through the diode 42, the base of the transistor 40 is driven positive with respect to its emitter, and this transistor is placed in a conductive condition so that an audi 3 ble annunciator or horn 48 which is connected between the emitter electrode of the transistor 40 and the negative potential source through a normally closed switch 50 and a resistance element 52 is energized to provide an audible indication of the alarm condition. The flow of current through the transistor 40 also produces a potential drop across the resistance element 44 so that the base of a second normally nonconductive transistor 54* inthe control means 22 is driven negative with respect to its emitter electrode. The emitter electrode is normally held negative with respect to the base by the current flow through a diode 56 and a resistance element 57 until the transistor 40 is placed in a conductive condition. When the transistor 54 is placed in'conduction, virtually the entire operating potential of the system appears across a collector resistance element 58. The potential developed across the resistance element 58 is returned directly to the base of the transistor 40 to hold this transistor in a conductive condition for as long as a collector potential is supplied thereto. This potential is also supplied to the multivibrator 18 to enable the operation thereof.

The multivibrator means 18 includes a pair of transistors 60 and 62 the collector and base electrodes of which are cross-coupled by a pair of capacitors 64 and 66.

The emitter of the transistor 60 is returned directly to the negative potential, and the emitter of the transistor 62 is supplied with a fixed potential by a voltage dividing network which is connected between the positive and negative potential sources and which includes a pair of diodes 68 and 70 and a resistance element 72. This voltage dividing network also applies a selected potential to the emitter of a normally nonconductive output tran sistor 74.

The collector of the transistor 62 is connected to the positive potential source through a pair of resistance elements 76 and 78. Since the drop across the diode 70 maintains the emitter of the transistor 62 at a more positive potential than the base of this transistor which is connected to the negative potential source through a re-,

sistance 80, the transistor 62 is normally maintained in a nonconductive condition. The collector and base of the transistor 60 are connected to the positive potential supplied'by the conductive transistor 54 by a pair of resistance elements 82 and 84, respectively.

When the transistor 54 is rendered conductive, the positive-going signal at its collector is'rorwarded through a diode 86 and a resistance element 88 to the base of the normally nonconductive transistor 62 .in the multivibrator 18. The potential provided through the diode 86 supplements the potential previously supplied through a diode 90 from the emitter of the transistor 24 in the in put stage 20 and drives the base of the transistor 62 positive with'respect to its emitter. This places the transistor 62 in a conductive condition so that the normally charged capacitor 66 drives the base of the transistor in a negative direction to insure that this transistor is in a nonconductive condition. When the transistor 62 is placed in a conductive condition, the base of the output transistor 74 is driven negative with respect to its emitter so that the transistor 74 is placed in a conductive condition. The collector of the transistor 74 is connected to a negative potential source through a pair of resistance elements 92 and 94, the common point of which is connected to the gate electrode of the gated silicon rectifier 16. Accordingly, when the transistor 74 is placed in a conductive condition, a positive-going gate signal isapplied to the gate electrode of the silicon rectifier 16 so that this unit, which is shunted by an oppositely poled diode 96, is placed in conduction during the proper half cycles of the SOO-cycle signals supplied by the source 14. This energizes the panel 12 to cause its luminescence, thereby providing a visible indication of the existence of the alarm condition.

More specifically, the circuit arrangement used to control the alternating current energization of the electroluminescent panel 12 represents a substantial advance a over prior circuits controlling alternating current loads, which prior circuits usually require a pair ,of controlled rectifiers with the attendantincrease in the cost and complexity of the circuit In the normal condition-of the circuit, the transistor 74 is in a nonconductive condition so that a gate signal is not suppliedto the controlled rectifier 16, and this component remains in a nonconductive state. The electroluminescent panel. 12, which has a very high directcurrentresistance and'an appreciable capacitance, is charged through the shunting diode 96 during the properly poled half cycle of the, applied alternating current potential from the source 14. During the other or oppositely poled half cycles of the potential from the source 14,!both the diode 96.,and the" controlled rectifier 16 are in a nonconductive state so that I a direct current potential equal to the peak voltage of the source 14 is applied between the electrodes of the panel 12. Since this panel is stimulatedto emit visible light only in response to alternating current excitation, no light sis produced by the. panel. 12 so long as only the diode' 96 and not the controlled rectifier 16 conducts.

However, when the transistor 74 isiplacedin a conductive condition in the manner described above to supply a gate current to the controlled rectifier 16, this rectifier and the diode 96 conduct on oppositely 'poledhalf cyclesof the potential supplied by the source 14,iand alternating current excitation is applied to the panel 12 to supply a light output.

The circuit 10 remains in the conditionin which the panel 12 is illuminated until the capacitor 66 discharges over a circuit including the'conductive transistor 62. At this time, the base ofthe transistor 60, by virtue of its connection through the resistance element 84 to the collector of the transistor 54, becomes positive with respectto its emitter electrode, andthe transistor" 60 is placed in a conductive condition. When the transistor 60. con: ducts, the coupling capacitor 64 drives the base of the transistor 62 negative with respect to its emitter electrode so that conduction through the transistor 62 is terminated. This removes theienabling potential from the base of the output transistor 74 so thatconduction through this transistor is terminated. This removes the gate signal from the silicon rectifier 16 so that, during the next period of reverse polarity, it is placed in a nonconductive condition to terminate the energizationof the electroluminescent panel 12.

When conduction through the transistor 62 is terminated, the capacitor 66 begins to charge and the capacitor 64 discharges over a path including the conductive transistor 60. When the charge on the capacitor 64 has dissipated to a sufiicientdegree,-the transistor 62'is again placed in conduction-,-and the coupling capacitor 66 drives the base of the transistor 60 in a negative direction to terminate conduction through this transistor. In this manner, the multivibrator 18 pulses the gate electrode of the silicon rectifier 16 through the output transistor 74 so thatthe electroluminescent panel12 Eis intermittently energized to provide a flashing visual indication of the a-larmconditionsignified by the opening of the contacts 28 or'theclosing of the: contacts 30.3 This flashing indication by the panel and the .audibleindication provided by the energized horn 48 are produced independent of the setting of the switch 46 for so long as the transistor 24 is held in a conductive condition by the field contacts 28 and 30 representing a persisting abnormality in the condition to be monitored.

The operation of the control system 10 is also independent of the setting of the switch 46 in those instances in which the switch 50 is operated to terminate the operation of the horn 48 during the persistence of the abnormay condition signified by the continued conductive state of the transistor 24. More specifically, with the switch 46-operated to close either thecontacts 46a or the contacts 46b, the opening of the contacts 50', asby manually actuating a switch, terminates the energization of the horn 48 so that the audible indication is terminated. In addition, the opening of the contacts 50 interrupts the emitter circuit for the transistor 40 so that this transistor returns to a nonconductive state. When the transistor 40 is placed in a nonconductive condition, the negative bias for the base of the transistor 54 is removed, and this transistor returns to a nonconductive state. Once the transistors 40 and '54 have been placed in nonconductive states, the reclosure of the contacts 50 cannot return these transistors to a conductive state regardless of the persistence'of the abnormal condition signified by the continuing conductive condition of the transistor 24.

When the transistors 40 and 54 are placed in a nonconductive state, the termination of conduction through the transistor 54 removes the potential drop across the resistance element 58 so that an operating potential is no longer supplied either to the transistor 60 or through the diode 86 to the base of the transistor 62. Thus, the transistors 60 and 62 no longer operate as a multivibrator. However, the continuing conductive condition of the transistor 2'4 forwards a positive potential through the diode 90 and the resistor 88 to the base of the transistor 62. This holds the transistor 62 in a continuous conductive condition so that the transistor 74 is maintained in a conductive condition. The transistor 74 thus applies a continuous gate current to the rectifier 16 so that the panel 12 is no longer intermittently illuminated or flashed but is maintained in a continuously energized condition so that a continuous visible indication is provided of the fact that the abnormality in the condition to be monitored persists even though the audible annunciator 48 has been silenced. However, when the abnormality is corrected so that the contacts 28 and 30 return to their normal conditions, conduction through the transistor 24 is terminated, and a positive potential is no longer supplied through the diode 90 to the base of the transistor 62. This returns this transistor and the transistor 74 to a nonconductive condition so that illumination of the panel is terminated. The control or monitoring system 10 is now in its normal condition.

The type or mode of signalling provided by the circuit 10 is dependent on the setting of the switch 46 in those instances in which the abnormal condition signified by the actuation of the field contacts 28 and 39 is corrected prior to the time at which the contacts 50 are opened to silence the audible annunciator or horn 48. If the switch 46 is in a setting in which the contacts 46a are closed and if the abnormality in the monitored condition is corrected prior to the time at which the contacts 50 are opened, the return of the transistor '24 to its normal nonconductive state removes the only source of operating potential for the transistors and 54 so that they return to a nonconductive state and terminate the energization of the horn 48. When the transistor 54 returns to a nonconductive state, the potential supplied to the transistor 60 through the resistance elements 82 and 84 is removed. Further, the nonconductive conditions of the transistors 24 and 54 removes the potential supplied to the base of the transistor 62 so that both of the transistors 62 and 74 return to a nonconductive condition. This removes the control signal supplied to the gated rectifier 16, and the panel 12 is no longer periodically energized to provide a flashing indication. Accordingly, when the switch 46 is set in a position in which the contacts 46a are closed and the abnormality in the condition to be monitored is cleared prior to the opening of the contacts 50, the clearing of the abnormality controls the circuit 10 to return to its normal condition.

When the switch 46 is in a setting in which the contacts 46b are closed, the correction of the abnormality prior to the opening of the contacts 50 does not restore the circuit 10 to a normal condition and a continuing indication is provided that an abnormality has been encountered. More specifically, when the field contacts 28 and 30 are restored to a normal condition to terminate conduction through the transistor 24, the transistors 40 and 54 remain in their previously conductive state because of the operating potential supplied thereto through the closed contacts 46b. Thus, the audible annunciator 48 remains in an energized condition, and the transistor 54 continue-s to supply operating potential to the transistor 60 through the resistance elements 82 and 84. Therefore, the circuit 10 remains in the condition in which the panel 12 is flashed and the annunciator 48 in energized even though the abnormality no longer exists. The circuit 14) is returned to a normal condition in the manner described above by opening the contacts 50.

Although the present invention has been described with reference to a single illustrative embodiment thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. An alarm and annunciator system comprising an electroluminescent annunciator panel, an alternating current potential source for energizing the panel, diode means connected between the source and the electroluminescent annunciator panel, rectifier means connected in parallel with and oppositely poled to the diode, said rectifier means including a control electrode, multivibrator means for supplying a control signal to the control electrode, and switching means controlled in accordance with a condition to be monitored and operable to place the multivibrator means in operation when an alarm condition is established.

2. An alarm and annunciator system comprising an electroluminescent annunciator panel, an alternating current potential source for energizing the panel, diode means connected between the source and the panel, a silicon rectifier connected in parallel with and oppositely poled to the diode, said rectifier having a gate electrode, a bistable circuit for supplying pulses to the gate electrode of the rectifier, and switch-ing means controlled in accordance with a condition to be monitored and operable to place the bistable circuit in operation.

3. An alarm system comprising an electroluminescent panel, an alternating current potential source, a controlled conduction device including a control electrode and adapted to supply energy from the potential source to the panel, pulse generating means for applying periodically recurring pulses to the control electrode, switching means controlled in accordance with a condition to be monitored and operable when an abnormal condition exists, and means including at least one controlled conduction means responsive to the condition of the switching means for controlling the application of pulses from the pulse source to the control electrode.

4. An alarm system comprising an electroluminescent panel, an alternating current potential source, diode means connected between the source and the panel, controlled rect-ifier means connected in parallel with and oppositely poled to the diode, said rectifier means including a gate electrode, multivibrator means coupled to the gate electrode to control conduction through the rectifier means, contact means operable in dependence on a condition to be monitored, and first controlled conduction means responsive to the contact means for supplying an enabling signal to the multivibrator means to place the multivibrator means in operation.

5. An alarm system for use with a condition to be monitored comprising an electroluminescent means for providing a visible display of an abnormality in the condition, a high frequency potential source for energizing the electroluminescent means, diode means connected between the source and the electroluminescent means, a controlled conduction device connected in parallel with and oppositely poled to the diode, said device having a control electrode, a signal source, and switching means controlled in accordance with the condition to be monitored and operable to render the signal source effective to supply signals to the control electrode of the controlled conduct-i on device so as to energize the electroluminescent means when an abnormality in the monitored condition arises.

6. An alarm system comprising an electroluminescent panel, analternating current potential source, controlled rectifier means including a gate electrode and adapted to connect the potential source to the panel, multivibrator means coupled to the gate electrode to control conduction through the rectifier means, contact means operable in dependence on a condition to be monitored, first'controlled conduction means responsive to the contact means for providing an output signal indicating the presence of an abnormal condition, means for forwarding the output signal to the multivibrator means to render this means effective, second controlled conduction means responsive to the output signal for also rendering the multivibrator means effective, and control means for selectively maintaining the conductive condition of the second controlled conduction means in dependence on the continuity ofthe output signal or triggering the second controlled conduction device to a condition of conduction in which. it remainstindependent of the continuity of the output signal.

7. An alarm system comprising anelectroluminescent panel, an alternating current potential source, controlled rectifier means including a gate electrode and adapted to connect the potential source to the panel, multivibrator means coupled to the gate electrode to control conduction through the rectifier means, contact means operable in dependence on a condition to be monitored, first controlled condu'ction means responsive to the contact means for supplying an enabling signal to the multivibrator means to place the multivibrator means in operation, and second controlled conduction means controlled by the first controlled conduction means, and operable to control the provision of an audible indication representing an abnormal condition.

8. An alarm system comprising an electroluminescent panel, an alternating current potential source, controlled rectifier means including a gate electrode and adapted to connect the potential source to the panel, multivibrator means coupled to the gate electrode to control conduction through the rectifier means, contact means operable in dependence on a condition to be monitored, first controlled conduct-ion means responsive to the contact means for supplying an enabling signal to the multivibrator means to place the multivibrator means in operation, and

control means operable to one setting to maintain the energization of the panel after an abnormal; condition and until reset and operable to another setting to energize the panel only during the interval in .which the abnormal condition persists.

9. An alarm system-forv use with a condition to be monitored comprising an electroluminescent means for providing a visible display of an abnormality in the condition, a high, frequency, potential source'for energizing the signal source eflEective to supply signals'to the control electrode of the controlled conduction device after an abnormality in the monitored condition has been encountered and'operable'to another setting to control the signal source to supply signals to the control electrode duringv theintervalin which the abnormality exists and terminating with the end of the abnormality.

10. In an indicating system, anelectroluminescent means, a source .of alternating current potential for energizing the electroluminescent means, diode means connected between the source and the electroluminescent means, rectifier means connected in;parallel with and oppositely poled to the diode, :said rectifier means including a control electrode, and control means for'supplying sig-.

nals to the control electrode to control the ,energization of the electroluminescent means by the source. 1

References Cited by the Examiner UNITED STATES PATENTS 2,909,668 10/1959 'Thurlby et al.- 340228 X 3,084,338 4/1963 Mauer et al. 340-2131 3,097,314 7/1963 Harriman 30788.5 3,107,349 10/1963 Sperry- 340-213.1 X 3,124,793 3/1964 Foster 340 -21'3.2 3,128,456 4/1964 Silliman et al. 34O'213.1 3,193,814 7/1965 Foster 340213.1 X 3,212,079 10/ 1965 Huttner 340213.1

NEIL C. READ, Primary Examiner.

R. M. ANGUS, Assistant Examiner. 

8. AN ALARM SYSTEM COMPRISING AN ELECTROLUMINESCENT PANEL, AN ALTERNATING CURRENT POTENTIAL SOURCE, CONTROLLED RECTIFIER MEANS INCLUDING A GATE ELECTRODE AND ADAPTED TO CONNECT THE POTENTIAL SOURCE TO THE PANEL, MULTIVIBRATOR MEANS COUPLED TO THE GATE ELECTRODE TO CONTROL CONDUCTION THROUGH THE RECTIFIER MEANS, CONTACT MEANS OPERABLE IN DEPENDENCE ON A CONDITION TO BE MONITORED, FIRST CONTROLLED CONDUCTION MEANS RESPONSIVE TO THE CONTACT MEANS FOR SUPPLYING AN ENABLING SIGNAL TO THE MULTIVIBRATOR MEANS TO PLACE THE MULTIVIBRATOR MEANS IN OPERATION, AND CONTROL MEANS OPERABLE TO ONE SETTING TO MAINTAIN THE ENERGIZATION OF THE PANEL AFTER AN ABNORMAL CONDITION AND UNTIL RESET AND OPERABLE TO ANOTHER SETTING TO ENERGIZE THE PANEL ONLY DURING THE INTERVAL IN WHICH THE ABNORMAL CONDITION PERSISTS.
 10. IN AN INDICATING SYSTEM, AN ELECTROLUMINESCENT MEANS, A SOURCE OF ALTERNATING CURRENT POTENTIAL FOR ENERGIZING THE ELECTROLUMINESCENT MEANS, DIODE MEANS CONNECTED BETWEEN THE SOURCE AND THE ELECTROLUMINESCENT MEANS, RECTIFIER MEANS CONNECTED IN PARALLEL WITH AND OPPOSITELY POLED TO THE DIODE, SAID RECTIFIER MEANS INCLUDING A CONTROL ELECTRODE, AND CONTROL MEANS FOR SUPPLYING SIGNALS TO THE CONTROL ELECTRODE TO CONTROL THE ENERGIZATION OF THE ELECTROLUMINESCENT MEANS BY THE SOURCE. 